What kind of poison is this hospital can't cure, requiring them to seek out the poisoner? At least by their medical common sense, they had never encountered such a situation in reality, which made everyone even more astonished by Zhang Yang’s words.

“Zhang Yang, just tell us directly, what poison has Old Wu taken?” Su Zhantao asked again, and the others all looked toward Zhang Yang. When Su Zhantao asked, they too became curious about the poison afflicting Wu Zhiguo, eager to learn from Zhang Yang exactly what it was. Even Wu Zhiguo himself was now looking at Zhang Yang.

“He’s been poisoned by a Gu toxin unique to the Southern Frontier. To be honest, this is the first time I’ve ever encountered this kind of poison!” “Gu toxin?” Su Zhantao repeated in surprise, and the others stared blankly at Zhang Yang. The term ‘Gu toxin’ was not unfamiliar to them; many had seen it on television or read about it in Wuxia novels where it frequently appeared. Whether on screen or in print, Gu toxin left a consistent impression on people. First, it was a specialty of the Southern Frontier, produced by certain ethnic minorities. Second, it was incredibly mystical—a Gu seed was implanted into a person’s body to control them. This led to many legends evolving around Gu toxins. Some devoted women were said to cultivate a Gu from childhood, implanting it in the man they loved. If that man betrayed her, she would have a way to punish him directly or even cause his death. Legends are just legends, and television is not entirely true. While poisoning a lover isn't unheard of, it’s absolutely impossible for the victim to remain poisoned yet controlled for such an extended period. However, Gu toxin does exist, just not as exaggerated as depicted on TV. Strictly speaking, it is a very rare form of live biological poison, and victims rarely survive without a specific antidote. Gu toxins are exceptionally rare, and the antidote for each type is different, leading many victims to die regretting their fate. This, in turn, has made Gu toxin even more mysterious.

“Zhang Yang, are you deliberately joking? Does such a poison really exist?” Wu Zhiguo looked at Zhang Yang, unable to stop himself from asking. He was the most concerned person in this scenario, as he was the one supposedly poisoned. After speaking, he took a few more sips of water; sweat was still beading on his forehead. He couldn't afford not to drink.

Zhang Yang smiled faintly. He suddenly grasped Wu Zhiguo’s arm. While it was true this was his first time seeing a Gu toxin, the ancient texts of the Zhang family contained records of them, and Zhang Yang was intimately familiar with those books. Wu Zhiguo’s symptoms perfectly matched the descriptions, which is why he dared to conclude it was a Gu toxin.

Zhang Yang held Wu Zhiguo’s arm with one hand and took out a silver needle with the other. He gripped Wu Zhiguo’s wrist tightly, momentarily slowing the blood flow to expose the bluish veins. Holding the needle, Zhang Yang carefully pricked Wu Zhiguo’s arm in several places. After a few jabs, a segment of a bluish vein suddenly bulged significantly. The raised area continued to shift, clearly indicating something was moving inside. Before long, a shrill, piercing scream even emanated from Wu Zhiguo’s arm. Seeing this bizarre and terrifying sight, everyone froze. Especially Wu Zhiguo; this was happening to him. If Li Ya hadn't caught him, he might have collapsed entirely.

“It’s real, the Gu toxin!” Huang Hai swallowed hard. After Zhang Yang forced the Gu out to reveal itself, he released Wu Zhiguo’s arm. He currently had no antidote and could not forcefully extract the parasitic creature. Forcible removal could kill the Gu, but it would also cost Wu Zhiguo his life.

“Zhang Yang, what on earth is going on? Save me, you must save me!” Looking at his now-recovered arm, Wu Zhiguo grew even more flustered, the sweat on his brow seemingly increasing. Everyone else looked toward Zhang Yang. By now, they believed his words—how could they not, having witnessed that terrifying parasite themselves?

“Don’t worry, if I can save you, I absolutely will, but you must cooperate. First, we need to find the person who poisoned you; only then will you have a chance at a cure!” Zhang Yang spoke slowly, and Wu Zhiguo nodded repeatedly. Seeing the bulge on his arm and hearing that dreadful sound, Wu Zhiguo now fully trusted Zhang Yang. He would naturally follow whatever Zhang Yang said.

“I ask you, within the last ten days, whom have you encountered that seemed strange? Pay special attention to anyone from the Southern Frontier!” Zhang Yang inquired gently. Although the Gu toxins shown on television were exaggerated, some elements held truth. Firstly, Gu insects indeed originated only in the Southern Frontier as a local specialty, but it wasn't exclusive to one minority group; people from many ancient tribes there knew how to use Gu insects to cast poisons. However, Gu toxins varied in strength. Common ones weren't fatal; some merely caused hallucinations or discomfort, dissipating naturally once the small parasite died inside the body. There were also powerful Gu, which could survive in the host body for longer periods, potentially becoming lethal—like the one Wu Zhiguo was afflicted with.

Based on Wu Zhiguo’s symptoms, he had likely been poisoned by a type called the ‘Gua Gu’ insect. This type of Gu toxin manifests as rapid weight loss and constant sweating. If no measures were taken, the person would be finished in fifteen days at most, dying incredibly emaciated, as if their flesh had been scraped away. Fifteen days was the maximum time; using tonics to accelerate the parasite would hasten death. Wu Zhiguo had been taking tonics, speeding up the Gu’s destructive power. Zhang Yang telling him seven days was actually the calculated maximum limit.

Hearing Zhang Yang, Wu Zhiguo first calmed his nerves, then meticulously recalled the past ten days. Recalling just the last ten days was straightforward; he remembered most of it. After a moment, he slowly shook his head and murmured, “I haven't met anyone from the Southern Frontier these past few days. However, my cousin visited Cailnan Province not long ago; that place is very close to the Southern Frontier!” Upon saying this, Wu Zhiguo’s own expression shifted. This cousin was also an important member of the family. But his status and standing were less significant than Wu Zhiguo's; Wu Zhiguo was the primary heir, placing the cousin third. These weren't the main points, though. Most importantly, Wu Zhiguo remembered that the person who had been most concerned about his illness these last few days and recommended a doctor was this very cousin. The cousin had never been so proactive before, leading Wu Zhiguo to feel moved, thinking his younger brother had matured and was finally showing care. Now, thinking back, his actions might have had ulterior motives.

“We should also look into the person who went to Cailnan Province. If your cousin only visited, he couldn't be controlling the Gu toxin himself. Were there any strangers suddenly around him?” Zhang Yang asked again. “Strangers? Yes!” Wu Zhiguo blurted out. His cousin had returned from Cailnan Province with a beautiful young woman, claiming she was his new girlfriend. Wu Zhiguo had even dined with them. The young woman said little, but her eyes were sharp, leaving a deep impression on him at the time, which is why he remembered her. Wu Zhiguo hadn't thought much of his cousin bringing back a girl from out of town; it was normal for rich young masters like them to date a few beauties; he’d done the same himself. Now, with Zhang Yang’s reminder, he immediately sensed something was amiss. His cousin had always been fiercely competitive. Normally, even if he had a new girlfriend, he would never flaunt her in front of Wu Zhiguo. For him to actively introduce a new partner and invite Wu Zhiguo to dinner was already abnormal.

“Could it be that he’s trying to harm me? Is the poisoner that woman from Cailnan?” Wu Zhiguo asked, his eyes wide, finding it hard to believe. The more he thought about it, the more convinced he became. His cousin had exhibited many abnormal behaviors recently, but he had simply ignored them. For instance, after his health deteriorated, the cousin was the most vehement opponent of Zhang Yang’s prescription, blaming Wu Zhiguo’s decline on Zhang Yang’s formula. Despite how reluctant he was to believe it, these abnormalities forced him to harbor suspicion. Living in a wealthy family, Wu Zhiguo knew better than anyone the competition within. It wasn't impossible that his cousin might secretly move against him for control of the family and its fortune. In fact, this possibility seemed quite high.

“If she was the only person from Cailnan you’ve seen recently, then she is the most likely suspect!” Zhang Yang nodded. Having a target was important. Unlike other poisons, Zhang Yang’s miraculous elixir could not save Wu Zhiguo; they had to find the poisoner. The elixir worked wonderfully for other illnesses or poisons, but it had zero effect on a Zhong poison. Gu toxin was a biological poison, also known as a living poison, and all its harm stemmed from the small Gu insect inside Wu Zhiguo. Though the Gu was small, it was a life form. If Wu Zhiguo consumed the elixir, it wouldn't cure the poison; instead, the Gu would absorb the medicinal power from his body, accelerating the Gu toxin’s onset. Simply put, the elixir that cured all ills was actually poison to Wu Zhiguo, who was afflicted by Gu.

“I’ll go back right now and question them thoroughly!” Wu Zhiguo gritted his teeth. It really might be this person. He had even given her a valuable gift upon their first meeting, only to find out she was there to harm him.

“Don’t rush. This person is crucial, but we need to confirm it before moving against her. In the meantime, we can seek confirmation from another individual!” Zhang Yang shook his head again. The others exchanged surprised glances.

“That old traditional Chinese doctor who prescribed the formula for Zhiguo. His prescription was a powerful tonic, something rarely used. Zhiguo’s initial symptoms didn't call for such a formula, yet he prescribed it—he clearly had another objective!” A faint smile touched Zhang Yang’s lips as he slowly explained. This so-called old Chinese doctor was definitely compromised. Finding him would reveal who was directing him. If it was indeed Wu Zhiguo’s cousin and that woman, things would be simpler: they could control them first. If not, they could avoid alerting the true poisoner and letting them escape.

………… Fourth update, 100 chapters bonus continuing with Chapter 73. .RT